1. Technical Field
The present invention relates to a long-period vibration sensor and a method for correcting an output value of the long-period vibration sensor.
2. Related Art
In the related art, there has been known a vibration detector for detecting long-period vibrations when the long-period vibrations occur due to an earthquake or the like.
For example, a pendulum-type quake detection sensor has been proposed as a vibration detector in Patent Document 1. The pendulum-type quake detection sensor includes a pendulum which is suspended from the ceiling of a building through a wire, and a sensor which is disposed under the pendulum. The sensor irradiates a lower surface of the pendulum with light and receives the light reflected by the lower surface.
In such a pendulum-type quake detection sensor, a reflection surface is formed in the lower surface of the pendulum so that the light quantity of light reflected by the reflection surface varies sequentially from the center of the pendulum toward the outside in accordance with the amplitude of the pendulum. Thus, the light quantity of light reflected by the lower surface of the pendulum is detected so that the amplitude of the pendulum can be detected from the light quantity.
Besides the pendulum-type quake detection sensor, for example, a servo-type accelerometer which can carry out measurement from a DC region (still state) has been proposed as a vibration detector.
Such a servo-type accelerometer detects a displacement of a movable portion disposed in a casing, due to an external force. The servo-type accelerometer measures acceleration by measuring the amount of a current which is proportional to the displacement when the current is applied to a coil for driving the movable portion in order to keep the movable portion in a still state.